Variances in fuel composition being supplied to an internal combustion engine can affect the engine's performance. If the fuel composition changes in a manner that affects the specific energy of the fuel or the stoichiometry of the combustion reaction, the amount of fuel supplied to the engine must be adjusted to maintain the engine's performance. Some engine systems compensate for variances in the fuel being supplied to the engine by sensing the fuel composition before combustion and effecting a predetermined fuel map for the particular fuel composition. Such systems, however, are generally configured to sense changes in only specific components of the fuel, for example, to sense the ratio of one fuel to another in a composite fuel. By sensing specific components of the fuel, these systems ignore other variances. These variances may have a substantial impact on the engine's performance.
Therefore, there is a need for an engine system that compensates for changes in fuel beyond variances in specific fuel components.